The present invention relates generally to gas turbine engines and, more particularly, to a bearing arrangement a gas turbine engine.
A gas turbine engine typically includes a high pressure spool, a combustion system and a low pressure spool disposed within an engine case to form a generally axial, serial flow path about the engine centerline. The high pressure spool includes a high pressure turbine, a high pressure shaft extending axially forward from the high pressure turbine, and a high pressure compressor connected to a forward end of the high pressure shaft. The low pressure spool includes a low pressure turbine, which is disposed downstream of the high pressure turbine, a low pressure shaft, which typically extends coaxially through the high pressure shaft, and a low pressure compressor connected to a forward end of the low pressure shaft, forward of the high pressure compressor. The combustion system is disposed between the high pressure compressor and the high pressure turbine and receives compressed air from the compressors and fuel provided by a fuel injection system. A combustion process is carried out within the combustion system to produce high energy gases to produce thrust and turn the high and low pressure turbines, which drive the compressors to sustain the combustion process.
Gas turbine engines used in certain applications, such as helicopters and industrial power generation, include a third spool that is a power spool. The power spool includes a power turbine, which is disposed downstream of the low pressure turbine, and a power shaft, which typically extends forward coaxially through the high and low pressure shafts. The power shaft provides torque that can turn, for example, a rotor or a generator.
The high and low pressure spools as well as the power spool include alternating cascades of stators and rotors in order to work on the primary fluid in the flow path. Because the stators are stationary but the rotors rotate, bearings are necessary to permit the relative motion. In order to enable precise rotation of the shafts while maintaining a reasonable overall engine length, bearings are sometimes positioned relatively close to one another.